So how come Jehovah can do anything but he still needs angels.
There is no actual proof that there is a God or that there are Angels. Those things are all part the explanation that Christians came to believe as it was passed down to them at infancy and when they were trusting and without the the reasoning skills to question nor the coping skills to deal with the consequences of having done so.
The myriad of angels is relating to what the ancients saw in the sky at night as stars.Revelation 5:11 ►New Living Translation
Then I looked again, and I heard the voices of thousands and millions of angels around the throne and of the living beings and the elders.
English Standard Version
Then I looked, and I heard around the throne and the living creatures and the elders the voice of many angels, numbering myriads of myriads and thousands of thousands,